The leading musculo-skeletal complaint that Americans have is non-specific low back pain. Studies regarding the etiology of this pain (see McKenzie, R. A., The Lumbar Spine, Mechanical Diagnosis and Therapy, New Zealand, 1981) suggest that a combination of several conditions may collectively contribute to pain onset. First, the lumbar spine is anatomically strongest with the normal lordotic (extension) curve maintained. Inspection of the lumbar spine reveals the structural components of the vertebral disc are strongest and most reliable on the anterior (front) side of the spine. Secondly, the soft tissue structures which support the lumbar spine are strongest on the anterior side of the spine. When and if pain occurs, this pain is most often associated with soft tissue structures of the lumbar spine. Extension theory suggests that most non-specific low back pain is the result of the cumulative stresses and strains which are placed upon the posterior aspect of the lumbar spine by a lifestyle in which individuals are most often found bending forward (flexion).
According to the work by McKenzie referred to above, the chief contributing factor to the etiology of nonspecific low back pain is sustained flexion strain in the seated position. Obviously, maintenance of the normal protective lordotic curve would be the easiest answer to a great deal of suffering. However, anyone who has tried to actively and consciously maintain this protective curve will attest to the fact that it is virtually impossible to remember to sit correctly all the time.
A further obvious approach to this problem has been to attempt to create sitting environments in which the normal protective lumbar curve is passively maintained. Contemporary examples of passive devices designed for this purpose include special pillows to be placed behind the lower back while sitting, adjustable lumbar support devices installed in automobile seats, knee chairs, chairs with special built-in lumbar support, and the like.
A discussion with any biking enthusiast will reveal that lower back pain is a very common complaint. Sitting is obviously essential to the activity of bicycle riding and the sustained flexion strain placed upon the lower back by the simple act of sitting on a bicycle is significant. In addition, the hazard to lower back health is greatly compounded by the addition stresses created by pedaling.